Silicon (Si), with a theoretical capacity of 3579 mA h/g (for Li3.5Si) has attracted enormous attention as high capacity anode material for rechargeable Li-ion batteries. However, fast capacity fade due to structural degradation (pulverization) has hampered its use. Nanostructured silicon materials can accommodate the volume changes produced by lithium intercalation/deintercalation. Nanostructured silicon has been prepared from silica and silicates under high-temperature reduction processes, such as by carbothermal reduction of silica at temperatures of at least 2000° C. Silicon has also been prepared by reduction of silica with magnesium vapor at 650° C. (Bao et al., Nature 2007, 446: 172). However, it is difficult to retain the desired microscale morphology of the silica reactant in silicon products obtained at high temperatures since pore collapse becomes problematic. Hence, a need exists for a safe, low-temperature method of producing porous silicon that retains the porous morphology of the starting material.